We’ll be setting our clocks back an hour this weekend as the return to standard time comes at 2 a.m. on Sunday, November 4.

In theory, we gain an hour of sleep. In practice, the time change can have a profound effect on our ability to get quality sleep.

Aurore Perrault, a post-doctoral researcher in neuroscience at Concordia’s PERFORM Centre, outlines some of the impacts of the time change.

Are we right in thinking the time change messes with our sleep?

Our brain is extremely flexible so it will actually adapt relatively quickly to these time changes (as opposed to the more “natural” changes experienced in polar regions). But it often takes three or four days of difficulty in either getting to sleep or waking, before we fully adjust to the time change. This adjustment period is particularly difficult in the spring when we set our clocks back an hour for daylight savings time (so we lose an hour of sleep).

What are the measurable effects of the time change on our bodies?

The time change will throw off our circadian rhythm. That’s a form of internal clock that controls periodic (or cyclical) variations in a variety of physiological function including the wake-sleep cycle, body temperature, hormone levels and blood pressure. And the impact of this disruption can be serious.

For example, studies have found a higher incidence of heart attacks as well as workplace or traffic accidents on the Mondays following these seasonal time changes. Again though, the effect is more pronounced with the spring time change and, again, not everyone will experience such serious negative impacts.

Some people find the early darkness hard to adjust to. Does it cause a form of seasonal depression?

Our circadian rhythm is regulated principally by our exposure to light. Our brain is synchronized to the passages between day and night. The shrinking daylight in the fall and winter will absolutely have a negative impact on our sleep systems and, more generally, on our overall health. It brings on increased complaints of fatigue, sleepiness and the kind of negative impact on mood that we qualify as seasonal depression.

Being short on sleep negatively impacts not only our mood and our functioning but also our immune system. Vitamin D from exposure to sunlight is indispensable for helping our bones absorb calcium. It also reinforces our immune system to help us better resist infections during the bitter cold of winter, when we are already at an increased risk of getting sick.

Can you share a few tips on how to adjust to the time change?

If someone has a hard time adjusting to time changes, the best practise is to progressively adapt to the shift between day and night. Concretely, this means setting your alarm clock back by 10 or 20 minutes a day in the lead-up to the time change. Also, try and increase your exposure to natural light — as opposed to blue screens! That light is the main regulator of our circadian rhythm, so get as much as you can to optimize sleep and daytime functioning.